Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Carbamates have important applications in industry. Conventional synthesis methods generally involve preparing carbamates by alcoholysis and aminolysis using phosgene as a raw material. Many countries have taken initiatives to find novel synthesis processes to gradually replace the methods that use phosgene. In addition, in recent years, environmental issues have resulted in increasing attention. In particular, the rise in carbon dioxide levels in the global environment has led to an increased desire to fix and comprehensively use carbon dioxide as a potential carbon resource, while ensuring energy conservation and emission reduction. As carbon dioxide is stable, non-toxic, non-corrosive, flame-retardant and easily processed, it is one of the most widely distributed, most abundant in storage and cheapest carbon resource.
Accordingly, a desire has been to use carbon dioxide to replace limited and non-renewable petrochemical resources by C1 synthetic reaction and to prepare useful compounds by various chemical conversions. Such use has both important application values and theoretical research significance. Methods for synthesizing organic carbamates in one step using carbon dioxide, organic amine and alcohol as raw materials have drawn interest. However, the activity of catalysts used in synthesizing organic carbamates is often poor for aliphatic amines. Aliphatic amines are cheaper to use and less toxic than aromatic amines. Consequently, there is a need for methods of preparing carbamates using carbon dioxide as a raw material and using a reusable, highly active, efficient and more inexpensive catalyst.